Alpha-amino-acids are the building blocks of proteins and are therefore essential for life itself. Amino acids can be either of the type found in protein of biological sources (so called naturally occurring) or can be of other types that are synthesized chemically (so called synthetic amino acids). Dipeptides made from amino acids of either the naturally occurring type or the synthetic type have a multitude of uses including use as a nutritional source or intermediates therefor and use as building blocks for various biologically active proteins (e.g., see for example, C. Y. Bowers, et. al., European Patent Application WO 87/06835). One particularly economically important use of certain dipeptides or derivatives thereof is their use as an artificial sweetener (e.g., see R. H. Mazur, A. Ripper, Dev. Sweeteners, 1, 125 (1979)).
Alpha-amino acids typically have one asymmetric carbon atom and therefore can be either in the L or D form. Dipeptides can therefore exist as either one or the other (or a mixture) of two diastereomeric forms. Each of the two diastereomeric forms of a dipeptide can exist as either one or the other (or as a pair) of two enantiomeric forms. For various applications and in particular for sweetness it is often desirable to have only one of the diastereomeric and enantiomeric forms of a dipeptide. Therefore processes which can produce a dipeptide in a single diastereomeric form and a single enantiomeric form are highly desirable.